Process for the preparation of a silica silicasol, silica silicasol and applications

Abstract

The application provides a preparation method of a silica silicon sol, the silica silicon sol and application, and the preparation method comprises the following steps: preparing a catalyst solution containing ultrapure water and an alkaline catalyst; preparing a first silicon source solution containing a first alkoxysilane, ultrapure water and a first hydrolysis catalyst; preparing a second silicon source solution containing a second alkoxysilane, ultrapure water, a second hydrolysis catalyst and a pore-forming agent, wherein the pore-forming agent comprises polyethylene glycol with a relative molecular mass of 200-10000; adding the first silicon source solution into the catalyst solution to perform a first reaction, thereby preparing a first system; adding the second silicon source solution into the first system to perform a second reaction, thereby preparing a second system; and introducing ozone into the second system to remove residual pore-forming agent, thereby preparing the silica silicon sol. The silica particles contained in the prepared silicon sol have a compact silica skeleton and at the same time have a suitable size pore structure on the surface.

Description

Technical Field

[0001] This application relates to the field of silica nanomaterial preparation technology, and in particular to the preparation method, silica sol, and applications of silica sol. Background Technology

[0002] With the ever-increasing performance demands of electronic products, the integration density of integrated circuits has also improved, entering the nanometer era. Simultaneously, higher requirements have been placed on electronic chip manufacturing processes. Metal contamination, organic contamination, and surface quality issues on silicon wafer surfaces severely impact the yield and performance of precision components, thus posing new challenges to wafer surface processing. Chemical mechanical polishing (CMP) is currently the only technology capable of achieving global planarization. One of its most important consumables, the polishing slurry, is primarily composed of high-purity silica sol. Currently, advanced CMP processes use sol-gel method-prepared sol-type silica particles as abrasives, offering the advantage of high polishing rates while maintaining low defect rates.

[0003] Currently, based on the preparation system, silica sols are mainly divided into alcohol-based silica sols and aqueous silica sols. Due to the completely different system properties during preparation, the properties of these two types of silica sols differ significantly. Alcohol-based silica sols have larger silica particle pores and a looser, softer silica framework. Under high polishing rates and pressures, the silica particles are crushed by the polishing pad, reducing polishing efficiency. Furthermore, the aggregation of broken particles significantly increases the risk of scratches. Aqueous silica sols, on the other hand, have harder, more compact silica particles with smaller pores and smoother surfaces. Debris generated during polishing cannot be absorbed into the pores, making them highly susceptible to severe localized scratches in advanced processes, thus reducing the polishing yield. Summary of the Invention

[0004] Based on this, this application provides a method for preparing silica sol, silica sol and its application, wherein the silica particles contained in the silica sol have both a dense silica framework and a surface with a suitable pore structure.

[0005] The first aspect of this application provides a method for preparing silica sol, comprising the following steps:

[0006] Prepare a catalyst solution containing ultrapure water and an alkaline catalyst;

[0007] A first silicon source solution comprising a first alkoxysilane, ultrapure water, and a first hydrolysis catalyst is prepared.

[0008] A second silicon source solution comprising a second alkoxysilane, ultrapure water, a second hydrolysis catalyst, and a pore-forming agent is prepared; the pore-forming agent comprises polyethylene glycol with a relative molecular mass of 200-10000.

[0009] The first silicon source solution is added to the catalyst solution to carry out a first reaction, thereby preparing a first system;

[0010] The second silicon source solution is added to the first system to carry out a second reaction, thereby preparing the second system;

[0011] Ozone is introduced into the second system to remove residual pore-forming agent, thereby preparing the silica sol.

[0012] In some embodiments, the pore-forming agent accounts for 100 ppm to 5000 ppm by mass, based on the total mass of the reaction system.

[0013] In some embodiments, the ozone is introduced below the liquid surface of the second system.

[0014] In some embodiments, the ozone mass percentage is 1000ppm-50000ppm based on the total mass of the reaction system.

[0015] In some embodiments, after ozone is introduced, the mixture is stirred at 70°C-90°C at a speed of 200r / min-1000r / min for 1-3 hours to remove residual pore-forming agent.

[0016] In some embodiments, the alkaline catalyst accounts for 3%-5% of the mass of the catalyst solution.

[0017] In some embodiments, the alkaline catalyst comprises one or more of alkali metal hydroxides, ammonia, and organic amines.

[0018] In some embodiments, the alkali metal hydroxide includes one or more of potassium hydroxide and sodium hydroxide.

[0019] In some embodiments, the organic amine includes one or more of ethylenediamine, triethanolamine, tetramethylamine hydroxide, and guanidine compounds; optionally, the guanidine compounds include one or more of tetramethylguanidine, trimethylguanidine, and guanidine carbonate.

[0020] In some embodiments, the first alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, and may be tetramethoxysilane.

[0021] In some embodiments, the mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is (5-10):1.

[0022] In some embodiments, the first hydrolysis catalyst includes one or more of acetic acid, malic acid, citric acid, and maleic acid.

[0023] In some embodiments, the mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is (100-500):1.

[0024] In some embodiments, the mass ratio of the first silicon source solution to the catalyst solution is (1-12):4.

[0025] In some embodiments, the second alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, and may be selected as tetramethoxysilane.

[0026] In some embodiments, the mass ratio of the ultrapure water to the second alkoxysilane in the second silicon source solution is (5-10):1.

[0027] In some embodiments, the second hydrolysis catalyst comprises one or more of acetic acid, malic acid, citric acid, and maleic acid.

[0028] In some embodiments, the mass ratio of the ultrapure water to the second hydrolysis catalyst in the second silicon source solution is (100-500):1.

[0029] In some embodiments, the mass ratio of the second silicon source solution to the first silicon source solution is (1-3):1.

[0030] In some embodiments, the first silicon source solution is added to the catalyst solution at a dropping rate of 0.1 g / s to 1 g / s.

[0031] In some embodiments, the second silicon source solution is added to the first system at a dropping rate of 0.1 g / s to 1 g / s.

[0032] In some embodiments, the reaction temperature of the first reaction is 70℃-90℃, the reaction time is 2 hours-4 hours, and the stirring speed is 200r / min-1000r / min.

[0033] In some embodiments, the reaction temperature of the second reaction is 70℃-90℃, the reaction time is 2 hours-4 hours, and the stirring speed is 200r / min-1000r / min.

[0034] In some embodiments, after the step of introducing ozone into the second system to remove residual pore-forming agent, the method further includes performing a post-treatment.

[0035] A second aspect of this application provides a silica sol comprising silica particles, the silica particles comprising a core and a shell located on at least a portion of the surface of the core, the surface of the shell having a porous structure.

[0036] In some embodiments, the average pore size of the pore structure is 6 nm-30 nm.

[0037] In some embodiments, the average particle size of the silica particles is 60nm-200nm.

[0038] In some embodiments, the thickness of the shell layer is 30nm-60nm.

[0039] In some embodiments, the mass percentage of silica particles in the silica sol is ≥20%.

[0040] The third aspect of this application provides the application of the silica sol prepared by the preparation method of the first aspect of this application or the silica sol of the second aspect of this application in the preparation of polishing fluid.

[0041] The above-mentioned method for preparing silica sol has at least the following beneficial effects:

[0042] (1) Low molecular weight polyethylene glycol is used as a pore-forming agent to prepare silica particles with a core-shell structure and a porous shell surface. The amount of pore-forming agent used is small and the efficiency is high. The pore size of the shell pore structure can be controlled by selecting polyethylene glycol with different molecular weights. When the relative molecular weight of polyethylene glycol is within 200-10000, the pore structure of the silica particle shell has a suitable pore size.

[0043] (2) Ozone is introduced to oxidize and decompose the pore-forming agent to remove it. This method requires a small amount of ozone and is highly efficient. The polyethylene glycol is eventually decomposed into water and carbon dioxide, and the ozone and carbon dioxide escape from the system. This does not introduce impurities that affect polishing and helps improve the purity of the silica sol. Compared with traditional methods such as template method, freeze-drying method, and phase separation method, it is not necessary to separate the particles for high-temperature calcination to remove the pore-forming agent and then disperse them back into the system, which effectively simplifies the process.

[0044] (3) The preparation method of this application uses ultrapure water as a solvent, without the need to add a large amount of organic solvent to dissolve the pore-forming agent. The silica particles in the prepared silica sol have greater hardness, a dense and hard core, and a porous shell that maintains strong hardness. At the same time, the porous structure can better adsorb the fine debris generated during the polishing process, reducing the local scratches caused by debris accumulation, thus taking into account both the speed and yield under the requirements of high-speed and high-pressure polishing.

[0045] (4) The silica sol prepared by the method of this application has high storage stability and is not easy to agglomerate and settle. The preparation method is simple and easy to adjust and control the particle size, particle size distribution and particle morphology of the obtained silica particles, which is conducive to using silica sols with different core-shell thicknesses or pore sizes according to different polishing rates required by different processes. Detailed Implementation

[0046] To facilitate understanding of this application, a more complete description of the application will be provided below with reference to relevant embodiments. Preferred embodiments of the application are given below. However, the application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0048] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0049] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0050] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0051] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0052] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0053] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0054] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0055] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0056] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, but sequentially is preferred.

[0059] Currently, based on the preparation system, silica sols are mainly divided into alcohol-based silica sols and water-based silica sols. Due to the completely different properties of the preparation processes, the properties of the two types of silica sols differ significantly. The preparation process of alcohol-based silica sols is relatively mature. Because the reaction temperature is low and the preparation is carried out in an alcohol-water environment, the prepared silica particles generally have larger pore sizes and a looser, softer silica framework. During gentler polishing, the porous structure of the particles can absorb some of the polishing debris. However, under high polishing rates and pressures, the silica particles are crushed by the polishing pad, reducing polishing efficiency. Simultaneously, the aggregation of broken particles significantly increases the risk of scratches. With the development of polishing slurries and abrasive silica sols, the preparation system using water as a solvent and hydrolysate as a silicon source has a much lower cost than organic preparation systems. Furthermore, silica sols prepared under high-temperature conditions have higher silica particle hardness, significantly improved polishing rate, and are less prone to crushing. At the same time, the preparation process is almost free of toxic, harmful, and dangerous Class A reagents. Therefore, this preparation system has been widely studied. However, silica sols prepared by water-based processes have high hardness and compactness, small particle pore size, and relatively smooth particle surfaces. During the polishing process, the debris formed cannot be adsorbed into the pores of the abrasive, which can easily lead to severe local scratches in advanced processes, reducing the polishing yield.

[0060] To address the aforementioned issues, this application provides a method for preparing silica sol using low molecular weight polyethylene glycol as a pore-forming agent and introducing ozone to remove the pore-forming agent. The silica particles in the prepared silica sol have a core-shell structure, with a compact core and a porous shell. By selecting polyethylene glycol of different molecular weights as pore-forming agents or adjusting the amount of pore-forming agent, silica particles with different pore sizes or degrees of porosity can be prepared, with a small scale-up effect and good batch-to-batch stability of particle morphology.

[0061] One or more embodiments of this application provide a method for preparing silica sol, comprising the following steps: preparing a catalyst solution containing ultrapure water and an alkaline catalyst; preparing a first silicon source solution containing a first alkoxysilane, ultrapure water and a first hydrolysis catalyst; preparing a second silicon source solution containing a second alkoxysilane, ultrapure water, a second hydrolysis catalyst and a pore-forming agent, wherein the pore-forming agent comprises polyethylene glycol with a relative molecular mass of 200-10000; adding the first silicon source solution to the catalyst solution to carry out a first reaction to prepare a first system; adding the second silicon source solution to the first system to carry out a second reaction to prepare a second system; and introducing ozone into the second system to remove residual pore-forming agent to prepare silica sol.

[0062] It should be noted that the first silicon source solution is added to the catalyst solution to carry out the first reaction to prepare the spherical core of the silica particles; the second silicon source solution is added to the first system to carry out the second reaction to form a shell with a porous structure on at least part of the surface of the spherical core.

[0063] As an example, the relative molecular mass of polyethylene glycol used as a pore-forming agent can be, but is not limited to, 200, 600, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, or any range between two of the above relative molecular masses. When the relative molecular mass of polyethylene glycol is within the above range, a shell with a porous structure can be prepared, and the low molecular weight will not cause significant changes in the viscosity of the system, thus preventing a decrease in sol stability. Optionally, the relative molecular mass of polyethylene glycol is 600, 1000, or 2000.

[0064] In the preparation of silica sol, a first silicon source solution is added to a catalyst solution to carry out a first reaction, and seed crystals are prepared as spherical nuclei. After the particles are generated, the feeding of the first silicon source solution is stopped, and a second silicon source solution containing polyethylene glycol is added as the growth material for porous shells. After aging for a period of time, the reaction temperature is lowered to room temperature, and ozone is continuously and slowly introduced under the liquid surface for a period of time to remove the residual polyethylene glycol during the pore-forming process. The amount and molecular weight of polyethylene glycol are adjusted to produce shells with different pore sizes. The amount of the second silicon source solution used for shell growth is adjusted to control the shell thickness. Then, a series of post-processing steps, such as solvent replacement with water, filtration, and concentration, are performed to obtain silica sol.

[0065] Understandably, the method for preparing silica sol in this application has at least the following beneficial effects:

[0066] (1) Low molecular weight polyethylene glycol is used as a pore-forming agent to prepare silica particles with a core-shell structure and a porous shell surface. The amount of pore-forming agent used is small and the efficiency is high. The pore size of the shell pore structure can be controlled by selecting polyethylene glycol with different molecular weights. When the relative molecular weight of polyethylene glycol is within 200-10000, the pore structure of the silica particle shell has a suitable pore size.

[0067] (2) Ozone is introduced to oxidize and decompose the pore-forming agent to remove residual pore-forming agent. This method requires a small amount of ozone and is highly efficient. Polyethylene glycol is eventually decomposed into water and carbon dioxide, and ozone and carbon dioxide escape from the system. This does not introduce impurities that affect polishing and is beneficial to improving the purity of the silica sol. Compared with traditional methods such as template method, freeze-drying method, and phase separation method, it is not necessary to separate the particles for high-temperature calcination to remove the pore-forming agent and then disperse them back into the system, which effectively simplifies the process.

[0068] (3) The preparation method of this application uses ultrapure water as a solvent, without the need to add a large amount of organic solvent to dissolve the pore-forming agent. The silica particles in the prepared silica sol have greater hardness, a dense and hard core, and a porous shell that maintains strong hardness. At the same time, the porous structure can better adsorb the fine debris generated during the polishing process, reducing the local scratches caused by debris accumulation, thus taking into account both the speed and yield under the requirements of high-speed and high-pressure polishing.

[0069] (4) The silica sol prepared by the method of this application has high storage stability and is not easy to agglomerate and settle. The preparation method is simple and easy to adjust and control the particle size, particle size distribution and particle morphology of the obtained silica particles, which is conducive to using silica sols with different core-shell thicknesses or pore sizes according to different polishing rates required by different processes.

[0070] It should be noted that the terms "first alkoxysilane," "second alkoxysilane," "first hydrolysis catalyst," "second hydrolysis catalyst," "first silicon source solution," "second silicon source solution," "first system," and "second system" mentioned in the context are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be interpreted as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed-ended limitation on quantity.

[0071] In some embodiments, the pore-forming agent accounts for 100 ppm to 5000 ppm of the total mass of the reaction system; for example, it can be, but is not limited to, 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, or any range between two of the above mass percentages. When the amount of pore-forming agent is within the above range, the silica particle shell in the prepared silica sol has a suitable density and does not affect the storage stability of the sol system.

[0072] It should be noted that the "total mass of the reaction system" mentioned in the context refers to the total mass of all materials added during the preparation of silica sol. For example, this includes the total mass of ultrapure water, alkaline catalyst, first alkoxysilane, first hydrolysis catalyst, second alkoxysilane, second hydrolysis catalyst, and pore-forming agent added during the preparation process.

[0073] As one possible implementation, ozone is introduced below the surface of the second system. This allows the ozone to come into full contact with the sol under stirring, oxidizing and removing the pore-forming agent, polyethylene glycol, to produce carbon dioxide and water.

[0074] In some optional embodiments, the ozone concentration, based on the total mass of the reaction system, is between 1000 ppm and 50000 ppm. For example, it can be, but is not limited to, 1000 ppm, 5000 ppm, 10000 ppm, 15000 ppm, 20000 ppm, 25000 ppm, 30000 ppm, 35000 ppm, 40000 ppm, 45000 ppm, 50000 ppm, or any range between two of the above concentrations. When the ozone concentration is within the above range, the ozone retains a large number of surface silanol groups while effectively removing polyethylene glycol, preventing a sharp reduction in the number of surface silanol groups and maintaining the performance and storage stability of subsequent polishing applications.

[0075] In some embodiments, after ozone is introduced, the reaction is carried out at 70°C-90°C with stirring at a speed of 200 r / min-1000 r / min for 1 hour to 3 hours to remove residual pore-forming agent. For example, the temperature can be, but is not limited to, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, or any range between two of the above temperatures. The stirring speed can be, but is not limited to, 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, or any range between two of the above speeds. The reaction time can be, but is not limited to, 1 hour, 2 hours, 3 hours, or any range between two of the above times.

[0076] In some embodiments, the alkaline catalyst accounts for 3%-5% of the mass of the catalyst solution; for example, it can be, but is not limited to, 3%, 3.5%, 4%, 4.5%, 5%, or any range between two of the above values. This is beneficial for preparing particles with suitable particle size while maintaining pH stability of the system.

[0077] As one possible implementation, the alkaline catalyst includes one or more of alkali metal hydroxides, ammonia, and organic amines.

[0078] In some alternative embodiments, the alkali metal hydroxide includes one or more of potassium hydroxide and sodium hydroxide.

[0079] As one possible implementation, the organic amine includes one or more of ethylenediamine, triethanolamine, tetramethylamine hydroxide, and guanidine compounds. Optionally, the guanidine compounds include one or more of tetramethylguanidine, trimethylguanidine, and guanidine carbonate.

[0080] In some embodiments, the first alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane. Optionally, the first alkoxysilane is tetramethoxysilane.

[0081] As one possible implementation, the mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is (5-10):1; for example, it can be, but is not limited to, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, or any range between two of the above mass ratios. When the mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is within the above range, it is beneficial for the complete hydrolysis reaction of the alkoxysilane and ensures that the solid content of the product is within a reasonable range.

[0082] In some exemplary embodiments, the first hydrolysis catalyst includes one or more of acetic acid, malic acid, citric acid, and maleic acid. Optionally, the first hydrolysis catalyst is acetic acid.

[0083] In some embodiments, the mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is (100-500):1; for example, it can be, but is not limited to, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, or any range between two of the above mass ratios. When the mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is within the above range, it is beneficial for the alkoxysilane to maintain a suitable hydrolysis rate and maintain hydrolysis efficiency, and it is also beneficial for improving the stability of the reaction system.

[0084] In one possible implementation, the alkaline catalyst comprises 3%-5% of the catalyst solution by mass; the mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is (5-10):1; the mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is (100-500):1; and the mass ratio of the first silicon source solution to the catalyst solution is (1-12):4. As an example, the mass ratio of the first silicon source solution to the catalyst solution can be, but is not limited to, 1:4, 2:4, 3:4, 4:4, 5:4, 6:4, 7:4, 8:4, 9:4, 10:4, 11:4, 12:4, or any range between two of the above mass ratios. This facilitates the preparation of particles with suitable particle size while maintaining a stable pH in the system.

[0085] As an example, the step of preparing a first silicon source solution containing a first alkoxysilane, ultrapure water and a first hydrolysis catalyst includes: stirring and mixing the first alkoxysilane, ultrapure water and the first hydrolysis catalyst in a water bath at 5°C-10°C to prepare the first silicon source solution.

[0086] In some embodiments, the second alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane. Optionally, the second alkoxysilane is tetramethoxysilane.

[0087] As one possible implementation, the mass ratio of ultrapure water to the second alkoxysilane in the second silicon source solution is (5-10):1; for example, it can be, but is not limited to, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, or any range between two of the above mass ratios. When the mass ratio of ultrapure water to the second alkoxysilane in the second silicon source solution is within the above range, it is beneficial for the complete hydrolysis reaction of the alkoxysilane and the solid content of the product is within a reasonable range.

[0088] In some embodiments, the second hydrolysis catalyst includes one or more of acetic acid, malic acid, citric acid, and maleic acid. Optionally, the second hydrolysis catalyst is acetic acid.

[0089] In some optional embodiments, the mass ratio of ultrapure water to the second hydrolysis catalyst in the second silicon source solution is (100-500):1; for example, it can be, but is not limited to, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, or any range between two of the above mass ratios. When the mass ratio of ultrapure water to the second hydrolysis catalyst in the second silicon source solution is within the above range, it is beneficial to prepare particles with suitable particle size while maintaining the pH stability of the system.

[0090] In one possible implementation, the mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is (5-10):1, and the mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is (100-500):1; the mass ratio of ultrapure water to the second alkoxysilane in the second silicon source solution is (5-10):1, and the mass ratio of ultrapure water to the second hydrolysis catalyst in the second silicon source solution is (100-500):1; the mass percentage of the pore-forming agent, based on the total mass of the reaction system, is 1ppm-50ppm; and the mass ratio of the second silicon source solution to the first silicon source solution is (1-3):1. For example, it can be, but is not limited to, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any range between any two of the above mass ratios. By adjusting the ratio of the second silicon source solution to the first silicon source solution during the preparation process, the relative thickness of the core and shell of the obtained silica particles can be controlled, thereby controlling the hardness of the silica particles. When the mass ratio of the second silicon source solution to the first silicon source solution is within the above-mentioned range, the ratio of the core diameter to the shell thickness of the silica particles in the prepared silica sol is within a suitable range, the silica particles have a suitable shell thickness, and thus the silica particles have a suitable hardness.

[0091] As an example, the steps for preparing a second silicon source solution containing a second alkoxysilane, ultrapure water, a second hydrolysis catalyst, and a pore-forming agent include: mixing the second alkoxysilane, ultrapure water, the second hydrolysis catalyst, and the pore-forming agent in a water bath at 5°C-10°C to prepare the second silicon source solution.

[0092] In some embodiments, the first silicon source solution is added to the catalyst solution at a dropping rate of 0.1 g / s to 1 g / s. For example, the dropping rate can be, but is not limited to, 0.1 g / s, 0.2 g / s, 0.3 g / s, 0.4 g / s, 0.5 g / s, 0.6 g / s, 0.7 g / s, 0.8 g / s, 0.9 g / s, 1 g / s, or any range between two of the above rates. A dropping rate within the above range provides suitable reaction efficiency and is beneficial for improving the stability of the reaction system. Optionally, the dropping rate is 0.5 g / s.

[0093] As one possible implementation, the second silicon source solution is added to the first system at a dropping rate of 0.1 g / s to 1 g / s. For example, the dropping rate can be, but is not limited to, 0.1 g / s, 0.2 g / s, 0.3 g / s, 0.4 g / s, 0.5 g / s, 0.6 g / s, 0.7 g / s, 0.8 g / s, 0.9 g / s, 1 g / s, or any range between two of the above rates. A dropping rate within the above range provides suitable reaction efficiency and also helps improve the stability of the reaction system. Optionally, the dropping rate is 0.5 g / s.

[0094] In some embodiments, the reaction temperature of the first reaction is 70℃-90℃; for example, it can be, but is not limited to, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, or any range between two of the above temperatures. This facilitates the full condensation of the silanol groups generated by hydrolysis to form a silicon-oxygen-silicon framework, while simultaneously improving the reaction equilibrium.

[0095] As one possible implementation, the reaction time of the first reaction is 2 to 4 hours; for example, it can be, but is not limited to, 2 hours, 3 hours, 4 hours or any range between the two of the above times.

[0096] In some optional embodiments, the stirring speed of the first reaction is 200 r / min to 1000 r / min; for example, including but not limited to 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min or any range between two of the above speeds.

[0097] It should be noted that the first reaction occurred as soon as the first silicon source solution was added to the catalyst solution. After the addition was completed, the reaction continued, and stirring was carried out throughout the entire first reaction process.

[0098] As one possible implementation, the reaction temperature of the second reaction is 70℃-90℃; for example, it can be, but is not limited to, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, or any range between two of the above temperatures. This facilitates the full condensation of the silanol groups generated by hydrolysis to form a silicon-oxygen-silicon framework, while simultaneously improving the reaction equilibrium.

[0099] As one possible implementation, the reaction time of the second reaction is 2 to 4 hours; for example, it can be, but is not limited to, 2 hours, 3 hours, 4 hours or any range between the two of the above times.

[0100] In some optional embodiments, the stirring speed of the second reaction is 200 r / min to 1000 r / min; for example, including but not limited to 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min or any range between two of the above speeds.

[0101] It should be noted that the second reaction occurred as soon as the second silicon source solution was added to the first system. The reaction continued after the addition was completed, and the mixture was stirred throughout the entire second reaction process.

[0102] In some embodiments, after the step of introducing ozone into the second system to remove residual pore-forming agent, the method further includes performing a post-treatment.

[0103] As a non-limiting example, the post-processing includes: concentrating the silica sol under reduced pressure at 10 kPa and 100 °C to approximately 20 wt%, thereby obtaining a concentrated silica sol. Then, while adding ultrapure water, the organic solvent is evaporated until an ultra-high purity silica sol with a mass concentration of 20 wt% is obtained.

[0104] One or more embodiments of this application provide a silica sol comprising silica particles, the silica particles comprising a core and a shell located on at least a portion of the surface of the core, the surface of the shell having a porous structure.

[0105] The silica particles in this application's silica sol are harder, with a compact and rigid core. While maintaining strong hardness, the porous structure can effectively adsorb fine debris generated during polishing, reducing localized scratches caused by debris accumulation. This balances the speed and yield required for high-speed, high-pressure polishing. Furthermore, it exhibits high storage stability and is not prone to aggregation and sedimentation.

[0106] In some embodiments, the average pore size of the pore structure is 6nm-30nm; for example, it can be, but is not limited to, 6nm, 8nm, 10nm, 12nm, 14nm, 16nm, 18nm, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, or any range between two of the above pore sizes.

[0107] In some embodiments, the average particle size of the silica particles is 60nm-200nm; for example, it can be, but is not limited to, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm or any two of the above particle sizes.

[0108] In some implementations, the shell thickness is 30nm-60nm. For example, it can be, but is not limited to, 30nm, 40nm, 50nm, 60nm, or any range between two of the above thicknesses.

[0109] As one possible implementation method, the mass percentage of silica particles in the silica sol is ≥20%.

[0110] One or more embodiments of this application provide the application of silica sol prepared by the above-described preparation method, or the application of the above-described silica sol, in the preparation of polishing slurries. The polishing slurry includes a polishing slurry used in chemical mechanical polishing processes.

[0111] The technical solutions of this application will be described in detail below with reference to specific embodiments. It should be understood that these embodiments are only for illustrating this application and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application first, or follow experimental manuals or conventional conditions in the field, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the field.

[0112] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. For temperature and time parameters, acceptable deviations due to instrument testing accuracy or operational precision are permissible.

[0113] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available or prepared using conventional methods. The sources and specifications of the main raw materials used in the following examples and comparative examples are shown in Table 1.

[0114] Table 1

[0115]

[0116] In Table 1, "*" indicates that no relevant information exists.

[0117] The parameter testing methods in the following embodiments and comparative examples are as follows:

[0118] The test method for solid content refers to HGT 2521-2008 Industrial Silica Sol;

[0119] The average pore size of the silica particle shell was obtained by BET measurement using the nitrogen adsorption method.

[0120] The shell thickness of the silica particles is calculated based on the difference between the final particle size and the core particle size. The specific testing method is as follows: After the first reaction to prepare the silica particle cores, a small sample is taken, and the particle size is measured to obtain the average core particle size D1; after the second reaction to prepare the silica particle shells, a small sample is taken, and the particle size is measured to obtain the average finished particle size D2; the shell thickness is then (D2-D1) / 2.

[0121] The particle size of the silica sol particles was measured using a Malvern Zetasizer Nano ZS90 particle size analyzer.

[0122] Example 1

[0123] Step S1, Preparation of catalyst solution: Mix 200g of ultrapure water and 10.5g of potassium hydroxide evenly to prepare the catalyst solution.

[0124] Step S2, Preparation of the first silicon source solution: 43.5g of ultrapure water, 8.7g of tetraethoxysilane and 0.44g of malic acid (first hydrolysis catalyst) are stirred at 5°C for 2 hours and mixed evenly to obtain the spherical core silicon source solution, i.e. the first silicon source solution.

[0125] Step S3, Preparation of the second silicon source solution: 130.5g of ultrapure water, 26.1g of tetrapropoxysilane, 1.32g of malic acid (second hydrolysis catalyst) and 0.05g of PEG 1000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0126] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 210.5g of catalyst solution at a feed rate of 1g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 70℃ and 800r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0127] Step S5, Preparation of the second system: 157.97g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 70℃ and 800r / min for 1h to obtain the second system.

[0128] Step S6: Introduce 11.9 ppm ozone below the liquid surface and react at 70℃ and 800 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particle shell structure in the silica sol is 6.9 nm.

[0129] Example 2

[0130] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0131] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0132] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (second hydrolysis catalyst), and 2.5g of PEG 1000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0133] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0134] Step S5, Preparation of the second system: 663.9g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0135] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 18.6 nm.

[0136] Example 3

[0137] Step S1, Preparation of catalyst solution: Mix 200g of ultrapure water and 8.5g of triethanolamine evenly to prepare the catalyst solution.

[0138] Step S2, Preparation of the first silicon source solution: 568g of ultrapure water, 56.8g of tetrapropoxysilane and 1.14g of citric acid (first hydrolysis catalyst) are stirred at 5℃ for 2h and mixed evenly to obtain the spherical core silicon source solution, i.e., the first silicon source solution.

[0139] Step S3, Preparation of the second silicon source solution: 568g of ultrapure water, 56.8g of tetrapropoxysilane, 1.14g of citric acid (second hydrolysis catalyst), and 7.3g of PEG 1000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0140] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 208.5g of catalyst solution at a feed rate of 0.2g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 80℃ and 200r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0141] Step S5, Preparation of the second system: 633.24g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 80℃ and 200r / min for 1h to obtain the second system.

[0142] Step S6: Introduce 497 ppm ozone below the liquid surface and maintain the temperature and rotation speed for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100°C until approximately 20% is obtained, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% and an average pore size of 24.3 nm is obtained.

[0143] Example 4

[0144] The preparation method of Example 4 is similar to that of Example 2, except that: in step S3 of Example 4, PEG 200 is used instead of PEG 1000 to prepare the second silicon source solution; the average pore size of the silica particle shell pore structure in the obtained silica sol is 11.9 nm; all other aspects are the same. Example 4 is detailed below:

[0145] Step S1: Preparation of catalyst solution: Mix 200g of pure water and 6.5g of ammonia water and stir evenly to prepare the catalyst solution.

[0146] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0147] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (hydrolysis catalyst), and 2.5g of PEG 200 are stirred at 5℃ for 2 hours to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0148] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution using a peristaltic pump at a feed rate of 0.5g / s to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0149] Step S5, Preparation of the second system: 663.9g of porous shell silicon source solution was added to the reaction system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0150] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 11.9 nm.

[0151] Example 5

[0152] The preparation method of Example 5 is similar to that of Example 2, except that: in step S3 of Example 5, PEG 600 is used instead of PEG 1000 to prepare the second silicon source solution; the average pore size of the silica particle shell pore structure in the obtained silica sol is 13.5 nm; all other aspects are the same. Example 5 is detailed below:

[0153] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0154] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0155] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (second hydrolysis catalyst), and 2.5g of PEG 600 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0156] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0157] Step S5, Preparation of the second system: Use a peristaltic pump to add 663.9g of porous shell silicon source solution to the first system to carry out the second reaction. After the addition is complete, the reaction is carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0158] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 13.5 nm.

[0159] Example 6

[0160] The preparation method of Example 6 is similar to that of Example 2, except that: in step S3 of Example 6, PEG 2000 is used instead of PEG 1000 to prepare the second silicon source solution; the average pore size of the silica particle shell pore structure in the obtained silica sol is 21.2 nm; all other aspects are the same. Example 6 is detailed below:

[0161] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0162] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0163] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (second hydrolysis catalyst), and 2.5g of PEG 2000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0164] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0165] Step S5, Preparation of the second system: 663.9g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0166] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particle shell structure in the silica sol is 21.2 nm.

[0167] Example 7

[0168] The preparation method of Example 7 is similar to that of Example 2, except that: in step S3 of Example 7, PEG 5000 is used instead of PEG 1000 to prepare the second silicon source solution; the average pore size of the silica particle shell pore structure in the obtained silica sol is 26.8 nm; all other aspects are the same. Example 7 is detailed below:

[0169] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0170] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0171] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (second hydrolysis catalyst), and 2.5g of PEG 5000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0172] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0173] Step S5, Preparation of the second system: 663.9g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0174] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 26.8 nm.

[0175] Example 8

[0176] The preparation method of Example 8 is similar to that of Example 2, except that: in step S3 of Example 8, PEG 10000 is used instead of PEG 1000 to prepare the second silicon source solution; the average pore size of the silica particle shell pore structure in the obtained silica sol is 29.1 nm; all other aspects are the same. Example 8 is detailed below:

[0177] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0178] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0179] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, 1.4g of acetic acid (second hydrolysis catalyst), and 2.5g of PEG 10000 are stirred at 5℃ for 2h to mix evenly as a porous shell silicon source solution, i.e., the second silicon source solution.

[0180] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0181] Step S5, Preparation of the second system: 663.9g of porous shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0182] Step S6: Introduce 250 ppm ozone below the liquid surface and react at 90℃ and 350 r / min for 3 hours to remove the pore-forming agent. Concentrate under reduced pressure at 10 kPa and 100℃ until approximately 20% concentration is achieved, yielding a concentrated silica sol. Then, while adding ultrapure water, evaporate until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 29.1 nm.

[0183] Comparative Example 1

[0184] The preparation method of Comparative Example 1 is similar to that of Example 2, except that: in step S3 of Comparative Example 1, polyethylene glycol 1000, a pore-forming agent, was not added when preparing the second silicon source solution; ozone was not introduced in step S6 to remove residual pore-forming agent; the average pore size of the silica particles in the obtained silica sol is 3.5 nm; all other aspects are the same. The details of Comparative Example 1 are as follows:

[0185] Step S1: Preparation of catalyst solution: Mix 200g of ultrapure water and 6.5g of ammonia water evenly to prepare the catalyst solution.

[0186] Step S2, Preparation of the first silicon source solution: 294g of ultrapure water, 36g of tetramethoxysilane, and 0.7g of acetic acid (the first hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the spherical core silicon source solution, i.e., the first silicon source solution.

[0187] Step S3, Preparation of the second silicon source solution: 588g of ultrapure water, 72g of tetramethoxysilane, and 1.4g of acetic acid (second hydrolysis catalyst) are stirred at 5°C for 2 hours to mix evenly as the shell silicon source solution, i.e., the second silicon source solution.

[0188] Step S4, Preparation of the first system: The spheroid silicon source solution was added to 206.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction was carried out at 90℃ and 350r / min for 1h to obtain a monodisperse spheroid solution, i.e., the first system.

[0189] Step S5, Preparation of the second system: 661.4g of shell silicon source solution was added to the first system using a peristaltic pump to carry out the second reaction. After the addition was complete, the reaction was carried out at 90℃ and 350r / min for 1h to obtain the second system.

[0190] Step S6: Concentrate the silica sol under reduced pressure at 10 kPa and 100°C until it reaches approximately 20%, obtaining a concentrated silica sol. Then, while adding ultrapure water, evaporate the sol until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 3.5 nm.

[0191] Comparative Example 2

[0192] Step S1, Preparation of catalyst solution: Mix 294g methanol, 200g water and 6.5g ammonia water evenly to prepare the catalyst solution.

[0193] Step S2, Preparation of the spherical core silicon source solution: Mix 294g of methanol and 36g of tetramethoxysilane evenly to prepare the spherical core silicon source solution.

[0194] Step S3, Preparation of shell silicon source solution: Mix 588g of methanol and 72g of tetramethoxysilane evenly to prepare the shell silicon source solution.

[0195] Step S4: The spheroid silicon source solution is added to 500.5g of catalyst solution at a feed rate of 0.5g / s using a peristaltic pump to carry out the first reaction. The reaction is carried out at 60℃ and 350r / min for 1h to obtain a monodisperse spheroid solution.

[0196] Step S5: Use a peristaltic pump to add 660g of shell silicon source solution to the monodisperse sphere core solution. After the addition is complete, react at 60℃ and 350r / min for 1h.

[0197] Step S6: Concentrate the silica sol under reduced pressure at 10 kPa and 100 °C until it reaches approximately 20%, obtaining a concentrated silica sol. Then, while adding ultrapure water, evaporate the sol until a silica sol with a mass concentration of 20% is obtained; the average pore size of the silica particles in the silica sol is 38.3 nm.

[0198] It should be noted that in the subsequent polishing application, a large number of silica particles in the silica sol prepared in Comparative Example 2 were crushed during the polishing process, and the particle size changed significantly before and after polishing. This indicates that the silica particles in the silica sol of Comparative Example 2 have relatively low hardness, failing to efficiently complete the polishing task. Furthermore, the accumulation of crushed particle debris also leads to increased scratches. The reason for this may be that during the preparation of silica sol in the methanol system, hydrolysis and condensation reactions occur simultaneously. The incomplete hydrolysis of the silicon source results in a large number of unreacted silanol groups, while the number of silicon-oxygen-silicon bonds that are beneficial for increasing particle strength is relatively small.

[0199] Comparative Example 3

[0200] The preparation method of Comparative Example 3 is similar to that of Example 2, except that in step S3 of Comparative Example 3, PEG 15000 is used instead of PEG 1000 to prepare the second silicon source solution; all other aspects are the same.

[0201] It should be noted that the silica sol obtained in Comparative Example 3 agglomerated and settled after about 2 hours of standing, which could not meet the requirements of the sol state.

[0202] Comparative Example 4

[0203] The preparation method of Comparative Example 4 is similar to that of Example 2, except that: in step S3 of Comparative Example 4, cetyltrimethylammonium bromide (CTAB) is used instead of PEG 1000 to prepare the second silicon source solution; and in step S6 of Comparative Example 4, high-temperature calcination is used to remove the pore-forming agent. Step S6 of Comparative Example 4 is detailed below:

[0204] Step S6: Concentrate the silica sol under reduced pressure at 10 kPa and 100°C until it reaches approximately 20%, obtaining a concentrated silica sol. Then, while adding ultrapure water, evaporate the sol until a silica sol with a mass concentration of 20% is obtained. Place the silica sol in a muffle furnace at 500°C, increasing the temperature at 2°C / min, and holding for 3 hours to obtain silica particles with an average pore size of 12.8 nm. However, these particles cannot be redispersed in an aqueous system to form a silica sol and cannot be used in the polishing process.

[0205] Comparative Example 5

[0206] The preparation method of Comparative Example 5 is similar to that of Example 2, except that in step S6 of Comparative Example 5, 2g of PEG hydrolase (PEG-DH) was added instead of the ozone decomposition of PEG under the liquid surface. Simultaneously, to maintain activity, the pH was adjusted to 7.0, and the sample was treated at 37°C for 18 hours. The resulting silica sol had an average pore size of approximately 18.2nm. However, due to the inability to effectively remove the enzymes, a large number of colonies formed during the storage of the silica sol, contaminating the sample.

[0207] The solid content, average pore size of the silica particle shell structure, average particle size of the silica particles, and thickness of the silica particle shell obtained in the above embodiments and comparative examples are shown in Table 2.

[0208] Table 2

[0209]

[0210] The results of Examples 1-8 show that by using low molecular weight polyethylene glycol as a pore-forming agent and using ozone oxidation to decompose and remove the residual pore-forming agent, silica particles with a core-shell structure and a suitable size pore structure on the shell surface can be prepared.

[0211] A comparison of the results from Examples 1-8 and Comparative Example 1 shows that when polyethylene glycol (PEG) is added as a pore-forming agent and ozone is used as an oxidant to remove residual pore-forming agent, the pore size of the silica particle shell structure in the silica sol undergoes a significant change. In Comparative Example 1, no pore-forming agent was added, and the average pore size of the silica particle shell structure synthesized under aqueous conditions was only about 3.5 nm. Examples 1-8 involved a core-shell structure manufacturing process, and during the shell synthesis process, the low molecular weight PEG was introduced as a pore-forming agent, occupying space. Subsequently, after ozone oxidation, the low molecular weight PEG decomposed to generate water and carbon dioxide. The pore size of the shell structure was significantly larger than that of the shell structure in Comparative Example 1, and the generated carbon dioxide and water had no effect on the system.

[0212] In Examples 1-3, the same polyethylene glycol was used as the pore-forming agent, but the amount of pore-forming agent added varied, resulting in different average pore sizes of the silica particle shell structures obtained in Examples 1-3. The difference between Examples 2 and Examples 4-8 lies in the use of polyethylene glycols with different molecular weights as pore-forming agents, leading to different average pore sizes of the silica particle shell structures obtained in Examples 2 and Examples 4-8. Therefore, it can be seen that the pore size of the silica particle shell structure in the obtained silica sol can be controlled by adjusting the molecular weight and amount of the pore-forming agent, polyethylene glycol.

[0213] The results of Examples 1-8 and Comparative Example 2 show that when only ultrapure water is used as a solvent and no organic solvent is added, the silica particles in the prepared silica sol are harder, the core is compact and hard, and the porous shell also has strong hardness.

[0214] A comparison of the results of Examples 2, 4-8 and Comparative Example 3 shows that when high molecular weight polyethylene glycol is used as a pore-forming agent, the high molecular weight polyethylene glycol affects the stability of the silica sol, leading to the aggregation of some nanoparticles.

[0215] The results of Example 2 and Comparative Examples 4-5 show that using polyethylene glycol as a pore-forming agent and using ozone to remove residual polyethylene glycol is beneficial for preparing silica sol that meets the application requirements of the polishing process. In addition, the silica sol has good biological stability and is not easily contaminated.

[0216] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0217] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing silica sol, characterized in that, Includes the following steps: Prepare a catalyst solution containing ultrapure water and an alkaline catalyst; A first silicon source solution comprising a first alkoxysilane, ultrapure water, and a first hydrolysis catalyst is prepared. A second silicon source solution comprising a second alkoxysilane, ultrapure water, a second hydrolysis catalyst, and a pore-forming agent is prepared; the pore-forming agent comprises polyethylene glycol with a relative molecular mass of 200-10000. The first silicon source solution is added to the catalyst solution to carry out a first reaction, thereby preparing a first system; The second silicon source solution is added to the first system to carry out a second reaction, thereby preparing the second system; Ozone is introduced into the second system. After the ozone is introduced, the mixture is stirred at 70℃-90℃ and a speed of 200r / min-1000r / min for 1 hour to 3 hours to remove the residual pore-forming agent and prepare the silica sol.

2. The method for preparing silica sol as described in claim 1, characterized in that, The pore-forming agent accounts for 100ppm-5000ppm of the total mass of the reaction system.

3. The method for preparing silica sol as described in claim 1, characterized in that, The ozone is introduced below the liquid surface of the second system; and / or, The ozone content is 1000ppm-50000ppm based on the total mass of the reaction system.

4. The method for preparing silica sol as described in claim 1, characterized in that, The alkaline catalyst comprises 3%-5% by mass in the catalyst solution; and / or, The alkaline catalyst includes one or more of alkali metal hydroxides, ammonia, and organic amines.

5. The method for preparing silica sol as described in claim 4, characterized in that, The alkali metal hydroxide includes one or more of potassium hydroxide and sodium hydroxide.

6. The method for preparing silica sol as described in claim 4, characterized in that, The organic amines include one or more of ethylenediamine, triethanolamine, tetramethylamine hydroxide, and guanidine compounds.

7. The method for preparing silica sol as described in claim 6, characterized in that, The guanidine compounds include one or more of tetramethylguanidine, trimethylguanidine, and guanidine carbonate.

8. The method for preparing silica sol as described in claim 1, characterized in that, The first alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane; and / or, The mass ratio of ultrapure water to the first alkoxysilane in the first silicon source solution is (5-10):1; and / or, The first hydrolysis catalyst comprises one or more of acetic acid, malic acid, citric acid, and maleic acid; and / or, The mass ratio of ultrapure water to the first hydrolysis catalyst in the first silicon source solution is (100-500):1; and / or, The mass ratio of the first silicon source solution to the catalyst solution is (1-12):

4.

9. The method for preparing silica sol as described in claim 8, characterized in that, The first alkoxysilane is a tetramethoxysilane.

10. The method for preparing silica sol as described in claim 1, characterized in that, The second alkoxysilane includes one or more of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane; and / or, The mass ratio of ultrapure water to the second alkoxysilane in the second silicon source solution is (5-10):1; and / or, The second hydrolysis catalyst includes one or more of acetic acid, malic acid, citric acid, and maleic acid; and / or, The mass ratio of ultrapure water to the second hydrolysis catalyst in the second silicon source solution is (100-500):1; and / or, The mass ratio of the second silicon source solution to the first silicon source solution is (1-3):

1.

11. The method for preparing silica sol as described in claim 10, characterized in that, The second alkoxysilane is tetramethoxysilane.

12. The method for preparing silica sol according to any one of claims 1 to 10, characterized in that, The first silicon source solution is added to the catalyst solution at a dropping rate of 0.1 g / s to 1 g / s; And / or, The second silicon source solution is added to the first system at a dropping rate of 0.1 g / s to 1 g / s; And / or, The first reaction temperature is 70℃-90℃, the reaction time is 2-4 hours, and the stirring speed is 200r / min-1000r / min; and / or, The second reaction is carried out at a temperature of 70℃-90℃, for a reaction time of 2-4 hours, and with a stirring speed of 200r / min-1000r / min.

13. A silica sol prepared by the preparation method according to any one of claims 1 to 12, characterized in that, The silica sol comprises silica particles, each silica particle including a core and a shell located on at least a portion of the surface of the core, the surface of the shell having a porous structure with an average pore size of 6 nm-30 nm.

14. The silica sol as described in claim 13, characterized in that, The average particle size of the silica particles is 60nm-200nm; and / or, The thickness of the shell layer is 30nm-60nm; and / or, The mass percentage of silica particles in the silica sol is ≥20%.

15. The use of the silica sol prepared by the preparation method according to any one of claims 1 to 12 or the silica sol according to any one of claims 13 to 14 in the preparation of polishing fluid.

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